Table 1.

Poisson model comparisons for females

	Any Eating Disorder		Anorexia Nervosa		Other Eating Disorder
	Deviance	DF	Deviance	DF	Deviance	DF
Model I. Agea	4270.3	131	1971.3	131	4379.6	131
Model II. Agea + Period (drift)b	631.0	130	405.9	130	673.0	130
Model III. Agea + Periodc	144.2	121	147.2	121	231.6	121
Model IV. Agea + Cohortd	2929.9	130	1412.5	130	2908.0	130
Model V. Agea + Period (drift)b + Cohortd	624.5	129	389.4	129	668.4	129
Model VI. Agea + Periodc + Cohortd	143.1	120	146.5	120	204.1	120
Model II vs. Model Ie	p < 0.001		p < 0.001		p < 0.001
Model III vs. Model IIe	p < 0.001		p < 0.001		p < 0.001
Model VI vs. Model IIIe	p = 0.31		p = 0.42		p < 0.001
Best-Fitting Model (overdispersion test results)f	Model III (p = 0.80)		Model III (p = 0.83)		Model VI (p = 0.06)

Abbreviations: DF = Degrees of Freedom

^aAge treated as categorical variable with levels for every year between 8 and 30 (inclusive). There is no reference level because model excludes an intercept term.

^bPeriod treated as an interval variable with the levels described in footnote c assigned integer values 0 – 10.

^cPeriod treated as categorical variable with levels [1987–1989] (reference level), [1990–1991], [1992–1993], [1994–1995], [1996–1997], [1998–1999], [2000–2001], [2002–2003], [2004–2005], [2006–2007], [2008–2009].

^d(Birth) Cohort treated as categorical variable with levels [1979–1990] (reference level), [1991–2001].

^ep-value based on chi-squared test comparing (residual) deviance and DF for Model A (less reduced model) versus Model B (more reduced model).

^fp-value based on (one-sided) test of H_1. Poisson model mean < variance (overdispersion) versus H_0. mean = variance (no overdispersion).